Out of bushes, yes. Standing on both sides of the issue, I can say with certainty that the double barrel is actually really easy to bully him out of if he or his team are not a direct threat. If he's setting them up to poke or repel people, it's actually probably the easiest interrupt in the world. If he's behind, there's especially no coming back because even if they screw up the disarm you're not doing enough damage to justify following up, and by then you're probably out of barrels.
If his team is backing him and they're more of a threat than yours, then he can easily start setting up combos because you won't be daring enough to try to defuse the first barrel because you'd likely wind up dying afterward. But I go Gnar all the time against GP because not only is it a very easy lane but disabling his barrels is a breeze - and once you've played GP once, you know every trick with hiding them in the bush as well as the radius. There's basically nothing an enemy could do to win. Honestly, I'd argue he's balanced right now if people would just give him a try before saying he's too strong - but if they have to nerf him, they have to give some kind of reliability back in exchange for a power cut because he's too fallible to justify removing another large chunk of his power.
